The present invention relates to medical devices. More particularly, the invention relates to a removable vena cava clot filter that can be percutaneously placed in and removed from the vena cava of a patient.
Filtering devices that are percutaneously placed in the vena cava have been available for over thirty years. A need for filtering devices arises in trauma patients, orthopedic surgery patients, neurosurgery patients, or in patients having medical conditions requiring bed rest or non-movement. During such medical conditions, the need for filtering devices arises due to the likelihood of thrombosis in the peripheral vasculature of patients wherein thrombi break away from the vessel wall, risking downstream embolism or embolization. For example, depending on the size, such thrombi pose a serious risk of pulmonary embolism wherein blood clots migrate from the peripheral vasculature through the heart and into the lungs.
A filtering device can be deployed in the vena cava of a patient when, for example, anticoagulant therapy is contraindicated or has failed. Typically, filtering devices are permanent implants, each of which remains implanted in the patient for life, even though the condition or medical problem that required the device has passed. In more recent years, filters have been used or considered in preoperative patients and in patients predisposed to thrombosis which places the patient at risk for pulmonary embolism.
The benefits of a vena cava filter have been well established, but improvements may be made. For example, filters generally may be configured to be self-expandable when they are deployed in the vena cava of a patient. Struts of a vena cava filter may be configured to move radially between an expanded state for engaging the walls of the vena cava and a collapsed state for filter delivery and retrieval. In the collapsed state, struts of the filter may be randomly housed within a delivery sheath. While moving between the expanded and collapsed states, the strut ends may cross over each other in random fashion causing a risk of entanglement. Entanglement during filter deployment may undesirably increase time duration of the procedure.